A novel colorimetric strategy for sensitive and rapid sensing of ascorbic acid using cobalt oxyhydroxide nanoflakes and 3,3′,5,5′-tetramethylbenzidine

In this work, cobalt oxyhydroxide nanoflakes (CoOOH nanoflakes) were reported to possess a high oxidizability toward TMB for the first time and based on which we have developed a new strategy for qualitative and quantitative detection of ascorbic acid (AA). In our design, CoOOH nanoflakes can directly oxidize 3,3',5,5'-tetramethylbenzidine (TMB) to oxTMB with an obvious blue color emerging, and AA can selectively inhibit the oxidation of TMB to oxTMB by resolving CoOOH nanoflakes to Co2+, resulting in a decrease in the absorbance of oxTMB and bleaching of blue color. As such, the concentration of AA could be identified very easily by UV-vis spectroscopy and bare eyes. Under optimal conditions, this sensing platform showed a highly sensitive response to AA with a detection limit of 142 nM and a short assay time of 5 min. This assay was also successfully used to quantify AA in human serum samples and practical food samples. Importantly, using this fabricated sensing strategy, we have further developed a paper based strip sensor for AA detection with satisfactory results, showing its great potential for point of care applications. (C) 2017 Elsevier B.V. All rights reserved.